Paolo Costa, president of the Venetian Port Authority, has accused the Venice in Peril Fund, of which I am chairman, of "sciacallaggio pseudo-scientifico" (pseudo-scientific profiteering) for having drawn attention to the danger to Venice of deep-dredging the channels through the lagoon as part of his plans for developing a major port at Marghera.

He must have forgotten that the Fund, a wholly apolitical and disinterested British charity that for over 40 years has donated money for the restoration of Venice, in 2001 initiated and financed a three-year investigation at the University of Cambridge into the state of scientific knowledge about the lagoon. We did this to try to introduce some clarity and objectivity into an area which, due to the polemics over the mobile barriers MOSE, had become confusing and misunderstood.

This study was led by Dr Tom Spencer, the distinguished scientist who is director of the Coastal Research Unit at Cambridge. In 2003, it culminated in a three-day conference in Cambridge attended by over 100 scientists from all over the world, which concluded that a system of mobile barriers was indispensable for Venice. Dr Spencer went on to co-edit the papers of this conference, which were all subjected to peer review, the guarantee of their scientific reliability: Flooding and Environmental Challenges for Venice and its Lagoon: State of Knowledge (Cambridge University Press, 2005).

I think that this is enough to establish Dr Tom Spencer's credentials for challenging in our Venice Report the statement in the Port Authority's submission to the Senate on 11 May 2009: "Now that the situation regarding the lagoon has completely changed and the problem of its hydraulic equilibrium is solved because it will be possible to manage it through the judicious use of the MOSE system, it is at last possible to describe precisely, and in terms that are respectful of environmental considerations, how the port of Venice will be able to take part in the development of port (and transport) activity in northern Italy, located as it is half way between the African and Asiatic coasts of the Mediterranean and eastern central Europe". Dr Spencer's comment on this is that MOSE is a flood control system; it does not have any role in controlling the longterm changes in the nature of the lagoon. The reason why his opinion is important is that the Port Authority dispatches all concern for the lagoon with this single statement.

The longterm changes to the lagoon are part of the reason why the water is now 23cm higher in Venice than in 1897, when the control point was established. Anyone with the least awareness of the structures of the historic city knows that the now constantly raised water level affects how the buildings are used, already rendering many ground floors uninhabitable. The damp and increased salinity are attacking the brickwork, the marble and even the mosaics of St Mark's. This is the true sickness that is eating away at the city; the floods are merely the fever. The Venetians of the Serenissima built their houses with stone bases because stone is less porous than brick. Now, the water level is reaching-in some cases has already overreached-these bases. This is an unprecedented situation in the history of Venice and the cost of maintaining the city is going to grow and grow. In fact, it is time that a longterm estimate of this future cost is attempted.

The relationship between the water and the buildings is going to get worse for reasons beyond our control. Archaeological evidence shows that Venice subsides about five cm a century, to which must be added the effects of climate change, however uncertain they may be at present.We should think very carefully before choosing to do anything that further interferes with the nature of the lagoon, or if we do so, we have to factor in the question of Venice's survival. How long do we want it to survive? For what we decide now will affect the answer to this question. Venice in Peril fully understands the economic and social importance of the port expansion project. Mr Costa threatens us with legal action; we, by contrast, think that it would be more fruitful for everyone if he would accept our invitation to a public discussion with international scientists specializing in this field. If he has evidence that the deep lagoon channels will not be damaging, we-and the world-will be pleased and relieved to see it. If, on the other hand, the evidence confirms that there is a danger to Venice, the scientists may be able to suggest a way of resolving the problem. We have demonstrated with our past project that both Venice in Peril and the Cambridge scientists have an open mind.

In conclusion, we must not forget that Venice is a Unesco World Heritage site, and that every Italian government has the duty to keep it safe. This duty is reinforced by Article 3 of Italy's Legislative Decree 152/2006 relating to the environment (as amended by Legislative Decree 4/2008). This says that every human activity legally relevant under the decree must conform to the principle of sustainable development in order to ensure that satisfying the needs of the present generation does not compromise the quality of life and opportunities of future generations". The decree goes on to reinforce this by stating that in comparative choices involving public and private interests, priority must be given to the interests of protecting the environment and the cultural heritage."